The present invention relates to a method and apparatus for automatically kerning type set on a photocomposing machine.
The printing industry has been undergoing a technological change from type set using brass strips as a mold for molten lead, to the use of photocomposing machines for photographically setting galley sheets which are then pasted up and used in a photo-offset process. In undergoing this change, some of the artistry formerly associated with the typesetting process was abandoned in the effort to automate the equipment. The desire to provide automatic machines having replaceable font strips conflicted with the flexibility associated with manual typesetting. Maximizing the utility of the machines has lead to design constraints related to the format of font strips and the aperture size and location within the machine.
Heretofore, these design constraints have made automatic kerning of type set on photocomposing machines unwieldy and have imposed undesirable constraints upon type designers in addition to complex constraints upon the format of font strips.
In a photocomposing machine using drum-mounted font strips, it is desirable to maximize the number of characters per font strip while minimizing the size of font strips so that the access time for each character is minimized without increasing the peripheral drum velocity. The basis for these constraints is the fact that the drum continues to rotate while characters are being strobed onto a print-receiving medium. The discharge lamps used in photocomposing machines are designed to have a minimal flash duration to decrease the amount of smear of the character due to drum movement. Any increase in drum peripheral velocity leads to an increase in character smear, resulting in an unaesthetic output. Heretofore, these constraints reduced the flexibility of type designers and consequently eliminated much of the artistry associated with typesetting when a photocomposing machine, rather than hot type, was used.